| Abstract from DBPedia | In geography, a plain is a flat expanse of land that generally does not change much in elevation, and is primarily treeless. Plains occur as lowlands along valleys or at the base of mountains, as coastal plains, and as plateaus or uplands. In a valley, a plain is enclosed on two sides, but in other cases a plain may be delineated by a complete or partial ring of hills, by mountains, or by cliffs. Where a geological region contains more than one plain, they may be connected by a pass (sometimes termed a gap). Coastal plains mostly rise from sea level until they run into elevated features such as mountains or plateaus. Plains are one of the major landforms on earth, where they are present on all continents, and cover more than one-third of the world's land area. Plains can be formed from flowing lava; from deposition of sediment by water, ice, or wind; or formed by erosion by the agents from hills and mountains. Biomes on plains include grassland (temperate or subtropical), steppe (semi-arid), savannah (tropical) or tundra (polar). In a few instances, deserts and rainforests may also be considered plains. Plains in many areas are important for agriculture because where the soils were deposited as sediments they may be deep and fertile, and the flatness facilitates mechanization of crop production; or because they support grasslands which provide good grazing for livestock.平野 （へいや） または平地 （へいち） とは、山地に対して、低く平らな広い地形のことを指す地理用語である。 (Source: http://dbpedia.org/resource/Plain) |
